Abstract: A local area network is disclosed including apparatus and methods for transferring data between a plurality of data processing resources ("agents") coupled to a cable. In the preferred embodiment, a plurality of agents are coupled to a common cable for data transmission and reception. An agent newly coupled to the cable dynamically assigns itself a unique address on the cable to which other agents may send data. Once an agent has been assigned a final address, it may then transmit to, and receive data from, other agents on the cable. An agent desiring to send data to a receiving agent follows a three step handshake, wherein the sending agent transmits an "RTS" signal and within a predetermined time must receive a "CTS"signal from the receiving agent. The sending agent then transmits a data frame within a predetermined time after the CTS signal is received. The failure to detect a return CTS signal within the predetermined time denotes a collision condition.

Abstract: Apparatus and methods are disclosed which are most advantageously used in conjunction with a digital computer to provide improved graphics capability. These techniques permit the representation and manipulation of any arbitrarily shaped image in terms of "inversion points". Inversion points defining a region are sorted and stored such that the region shape may be regenerated at a later time from the inversion points. Means are provided to compare existing regions and new regions to be displayed, and region operators are provided to specify a precedence between the existing and new regions. Thus, new regions are appropriately "clipped" such that only portions of a new region may actually be displayed to achieve the desired graphic representation.

Abstract: The robotic assembly of a keyboard using a multiplicity of keys of a plurality of distinct types, such As key caps on a sculptured keyboard, can be substantially increased in speed by the use of a multifacted rotatable turret for picking up and installing the key caps onto the keyboard. A programmable robot, having a robotic arm is provided with a rotatable multifaceted turret. Each facet of the turret includes a key handling member which is molded to accept a distinct type of sculptured key. The types of sculptured keys are segregated in a pick-up position. The turret is manipulated by the robotic arm in the pick-up position to pick up a multiplicity of keys of one given type on each of the facets of the turret. Thus, each turret picks up one type of keys. The turret is then translated by the robotic arm to an assembly position. The turret is once again rotated and advanced to assemble the key caps on to key stem projected from the keyboard.

Abstract: The present invention provides methods and apparatus for improved error detection in a data processing system. The techniques of the present invention insure that there is a high probability that an error in a record of data (each record comprising a plurality of data bits) is detected. In the event of an error, the present invention applies a randomizing function to the error which modifies subsequent bits within the record and then propagates and further randomizes the error throughout the record to magnify its apparent size. The randomizing and propagation of the error significantly lowers the misdetection probability for random errors within a record, in that error detectability is no longer pattern sensitive. The use of both propagation and randomization functions significantly alters the data containing an error, such that a high probability of detection using check-sum techniques exists.

Abstract: A microcomputer system with video display capability, particularly suited for small business applications and home use is described. The CPU performance is enhanced by permitting zero page data to be stored throughout the memory. The circuitry permitting this capability also provides a pointer for improved direct memory access. Through unique circuitry resembling "bank switching" improved memory mapping is obtained. 4-bit digital signals are converted to an AC chroma signal and a separate luminance signal for display modes. Display modes include high resolution modes, one of which displays 80 characters per line.

Abstract: An improved switch assembly is disclosed, having particular application as part of a key in a computer keyboard. The switch includes a housing including a base, having electrical contacts secured above the base of the switch housing. A generally flat and deformable electrically conductive spring having a central area with outwardly extending spiral arms is disposed above the electrical contacts. A keystem is slidably mounted for longitudinal movement within the housing above the flat spiral spring. A user activates the switch by depressing a key cap mounted to the keystem, which deforms the spiral spring downward and forcing a portion of the spring against the electrical contact, thereby completing the circuit. The keystem includes outwardly extending tapered cam nubs. A "hairpin" cam spring is provided which in an inactive state rests in an oversize slot below the outwardly extending keystem cam. The depression of the key cap forces the tapered cam to spread the cam spring.

Abstract: A heat dissipating connector for semiconductor package leads is disclosed. The body of the connector is comprised of two oppositely facing fingers formed from a unitary strip by making a 180 degree bend transverse to the longitudinal axis of the strip. A heat dissipating fin is formed integrally with an edge of one of the fingers, and protrudes substantially perpendicular to the vertical centerline of the heat dissipating connector body. In its installed condition, the facing surfaces of the fingers engage a semiconductor package lead with a spring force urged from the spring configuration of one of the fingers. The integrated circuit electrical lead, when mounted between the engaging surfaces of the oppositely facing fingers, is gripped in place, thereby maintaining a good heat and electrically conductive relationship therewith.

Abstract: A floppy disk drive with automatic disc clamping and ejection is disclosed. The movement of the linear actuator is used to provide both the clamping and ejection, without other drive means. A pair of magnetic heads, positioned on opposing sides of a drive wheel, are fixed to a carriage, one engages the upper surface of the disc, the other the lower surface. Neither head moves relative to the other. The drive components are easily assembled providing a relatively inexpensive, yet reliable drive.